Casing for battery pack and battery pack

ABSTRACT

The present disclosure relates to a casing for a battery pack and a battery pack. The casing has a receiving space and an opening in communication with the receiving space, the receiving space is formed by a wall portion of the casing, and the wall portion is formed from two or more stacked base plates, between which a plurality of cavities are formed. By forming a plurality of cavities in the wall portion, the casing for a battery pack provided by the present disclosure not only can improve the bearing capacity and the impact resistance of the casing, but also can achieve a thermal management of the battery assembly by filling the plurality of cavities with a phase change material or cooling liquid, which can further improve the mechanical property of the casing with a relatively light weight and relatively high reliability.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/427,934, filed on May 31, 2019, which claims priority to ChinesePatent Application No. 201811362042.4, filed on Nov. 15, 2018, both ofwhich are hereby incorporated by reference in their entireties.

TECHNICAL FIELD

The present disclosure relates to a technical filed of power battery,and particularly to a casing for a battery pack and a battery pack.

BACKGROUND

With the rapid development of the electric vehicle industry, the demandfor power batteries is increasing, and the performance requirements ofpower batteries are also increasing. As a core component of the electricvehicle, safety, endurance and charging efficiency of the power batterysystem directly affect the vehicle performance and service life of theelectric vehicle.

In the prior art, the casing of the power batteries is usually made of asheet metal member or a cast aluminum member because it needs to bearthe weight of the batteries. However, during the running of the vehicle,the batteries will be subjected to various external impacts, and thecasing will directly transmit the external impact force to the batterieswhen subjected to the external impacts, which may bring wear and ruptureto the batteries, in the long run, and a safety accident may occur.

SUMMARY

The object of the embodiments of the present disclosure is to provide acasing for a battery pack and a battery pack, wherein the casing hasgood bearing capacity and impact resistance.

On one aspect, the embodiments of the present disclosure provide acasing for a battery pack, wherein the casing has a receiving space andan opening in communication with the receiving space, the receivingspace is formed by a wall portion of the casing, and the wall portion isformed from two or more stacked base plates, between which a pluralityof cavities are formed.

According to one aspect of the embodiments of the present disclosure,the base plates comprises a first base plate and a second base plate,and the cavity is formed by an outwardly projecting convex wall of thesecond base plate and a flat wall of the first base plate correspondingto the convex wall.

According to one aspect of the embodiments of the present disclosure,the first base plate and the second base plate are stacked in adirection from the receiving space to an exterior of the casing.

According to one aspect of the embodiments of the present disclosure,the convex wall comprises a top portion and a side portion connected tothe top portion, wherein the top portion is planar or curved, and thereis a smooth transition between the top portion and the side portion.

According to one aspect of the embodiments of the present disclosure,the wall portion has a wall thickness tin a range of 1 mm≤t≤6 mm, aratio of a wall thickness t1 of the flat wall to a wall thickness t2 ofthe convex wall is in a range of 0.5≤t2/t1≤1, the cavity has a height hin a range of h≤5×t1, and a ratio of the height h to a width W of thecavity is in a range of h/W≤0.5.

According to one aspect of the embodiments of the present disclosure,the wall portion comprises a bottom wall and side walls surrounding thebottom wall on a peripheral side of the bottom wall, and the bottom walland the side walls are integrally formed.

According to one aspect of the embodiments of the present disclosure, aminimum distance d from an intersection line between two adjacent sidewalls to the cavity is equal to or greater than 25 mm.

According to one aspect of the embodiments of the present disclosure,the plurality of cavities are in communication with each other to form aflow passage.

According to one aspect of the embodiments of the present disclosure,the casing is provided with an inlet pipe and an outlet pipe on the sidewall, wherein the inlet pipe and the outlet pipe are respectively incommunication with two ends of the flow passage, and are located at asame side of the side wall.

According to one aspect of the embodiments of the present disclosure, amaterial of the base plate has a tensile strength σ≥100 MPa, and has anelongation at break ≥12% and preferably ≥20%.

According to one aspect of the embodiments of the present disclosure,the cavities are formed between the first base plate and the second baseplate by a blow molding process.

On a further aspect, the embodiments of the present disclosure furtherprovide a battery pack, comprising: a battery assembly; a casingaccording to any one of the above embodiments; and a cover closing theopening of the casing to form an enclosed space for accommodating thebattery assembly together with the receiving space of the casing.

By forming a plurality of cavities in the wall portion, the casing for abattery pack provided by the embodiments of the present disclosure notonly can improve the bearing capacity and the impact resistance of thecasing, but also can achieve a thermal management of the batteryassembly by filling the plurality of cavities with a phase changematerial or cooling liquid, which can further improve the impactresistance and mechanical property of the casing with a simplestructure, light weight and high reliability. Further, the battery packprovided by the embodiments of the present disclosure uses the casing asdescribed above, which can improve the safety of the battery pack.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, advantages, and technical effects of exemplary embodiments ofthe present disclosure will be described below with reference toaccompanying drawings.

FIG. 1 is a schematic view showing a structure of a battery packaccording to an embodiment of the present disclosure;

FIG. 2 is a schematic view showing a structure of a casing for a batterypack shown in FIG. 1 viewed from one angle;

FIG. 3 is a schematic view showing the structure of the casing shown inFIG. 2 viewed from another angle;

FIG. 4 is a cross-sectional view of the casing shown in FIG. 3 takenalong the line A-A;

FIG. 5 is an enlarged schematic view showing a structure of the region Bin the cross-sectional view shown in FIG. 4;

FIG. 6 is a schematic view showing a structure of a flow passage formedby a plurality of cavities in the casing shown in FIG. 3;

FIG. 7 is a cross-sectional view of the casing shown in FIG. 6 takenalong the line C-C;

FIG. 8 is a schematic view showing a structure of another casing for thebattery pack shown in FIG. 1;

FIG. 9 is a cross-sectional view of the casing shown in FIG. 8 takenalong the line D-D;

FIG. 10 is an enlarged schematic view showing a structure of the regionE in the cross-sectional view shown in FIG. 9; and

FIG. 11 is an enlarged schematic view showing a structure of the regionF in the casing shown in FIG. 8, wherein:

-   -   1—casing;    -   10—receiving space;    -   11—wall portion;    -   111—bottom wall;    -   112—side wall;    -   113—spherical corner;    -   12—brim portion;    -   13—inlet pipe;    -   131—mounting step;    -   132—welding step;    -   14—outlet pipe;    -   15—support member;    -   16—protective member;    -   20—cavity;    -   21—first base plate;    -   211—flat wall;    -   22—second base plate;    -   221—convex wall;    -   2211—top portion;    -   2212—side portion;    -   30—island;    -   2—battery assembly;    -   3—cover;    -   R—flow passage;    -   R1—inflow confluence region; and    -   R2—outflow confluence region.

In the drawings, the same members are denoted by the same referencenumerals. The drawings are not drawn to scale.

DETAILED DESCRIPTION

Features and exemplary embodiments of various aspects of the presentdisclosure will be described in detail below. In the following detaileddescription, numerous specific details are set forth to provide a fullunderstanding of the present invention. However, it will be apparent tothe person skilled in the art that the present invention may bepracticed without some of the details. The following description of theembodiments is merely provided to provide a better understanding of theinvention by showing examples of the invention. In the figures and thefollowing description, at least some of the known structures andtechniques are not shown to avoid unnecessarily obscuring the presentinvention; and, for clarity, the size of a portion of the structure maybe exaggerated. Furthermore, the features, structures, orcharacteristics described hereinafter may be combined in any suitablemanner into one or more embodiments.

The orientations in the following description refers to the directionsas shown in the figures, and are not intended to define the specificstructure of the present invention. In the description of the presentdisclosure, it should be noted that, unless otherwise stated, the terms“installation”, “connected to”, and “connected with” are to beunderstood broadly, and may be, for example, a fixed connection, adisassemble connection, or an integral connection; they can be connecteddirectly or indirectly through an intermediate medium. The specificmeaning of the above terms in the present disclosure can be understoodby the person skilled in the art according to actual circumstance.Further, the terms “first”, “second”, and the like are configured fordescriptive purposes only and are not to be construed as indicating orimplying relative importance or implying the number of indicatedtechnical features. Therefore, the terms “first”, “second”, and the likemay indicate or imply including at least one indicated technicalfeatures.

For better understanding the present disclosure, a casing for a batterypack and a battery pack according to the embodiments of the presentdisclosure will be described in detail below by reference to FIG. 1 toFIG. 11.

Referring to FIG. 1, FIG. 2 and FIG. 3 together, embodiments of thepresent disclosure provide a battery pack comprising: a casing 1, abattery assembly 2 and a cover 3. The cover 3 and the casing 1 form anenclosed space for accommodating the battery assembly 2.

In an embodiment of the present disclosure which provides the casing 1for a battery pack, the casing 1 has a receiving space 10 and an openingin communication with the receiving space 10, and the receiving space 10is formed by a wall portion 11 of the casing 1. The wall portion 11 isformed by two or more stacked base plates, between which a plurality ofcavities 20 are formed.

The casing 1 can be formed by pressing metal base plates. Generally, thebattery assembly 2 and management system thereof in the battery packhave a weight of 200 Kg or more, and the wall portion 11 formed bypressing the metal base plates has a wall thickness t in the range of 1mm≤t≤6 mm. If t<1 mm, the wall portion 11 of the casing 1 is too thin tobear the battery assembly 2 and other components in the battery pack,and is easily broken during use. If t>6 mm, the casing 1 occupies a toolarge volume, which is not conducive to increase of an energy density ofthe battery pack. In order to increase a structural strength of thecasing 1 with a limited occupation space, a plurality of cavities 20 areformed between the two or more base plates to enhance the structuralstrength and bearing capacity of the casing 1.

Compared with the technical solution of providing reinforcing ribs onthe wall portion 11 of the casing 1, such a configuration not only canimprove a rigidity and strength of the casing 1, but also can improve avibration and impact resistance of the casing 1 by the cavities 20. Inthe situation that the battery pack is subjected to an external impact,the cavities 20 can absorb and disperse part of the external impactforce, thereby producing an effect of buffer and damping, and thusimproving an impact resistance of the entire battery pack. Further,compared with a member with cavities formed by a cast aluminum extrusionprocess, such a configuration can reduce the space occupied by thecasing. That's because due to the limitation of the casting process, themember with cavities formed by the casting process generally has a wallthickness greater than 3 mm, and thus a casing with an internal cavityformed by the casting process will have a wall thickness of at least 6mm, and accordingly will occupy a large space, which is not conducive tothe increase of the energy density of the battery pack.

Further, for an electric vehicle using power batteries, an operatingenvironment temperature generally falls within a range from −30° C. to80° C. An optimal operating environment temperature of the powerbatteries is in a range from 20° C. to 40° C., in which the powerbatteries have a best charge and discharge performance and a longestservice life, and there is a risk of short circuit when charging thepower batteries below 0° C. Therefore, a reasonable battery thermalmanagement design is critical to the performance and service life of thepower batteries.

For this purpose, the plurality of cavities 20 in the wall portion 11 ofthe casing 1 may be filled with a heat conductive material, such as butnot limited to, a phase change material having a solid-liquid transitiontemperature or a cooling liquid, to realize the thermal management ofthe battery assembly 2. Compared with the prior art in which the thermalmanagement of the battery assembly 2 is generally performed by abuilt-in/external water-cooling system, such a configuration is simple,occupies a small space, and does not need many pipe joints, which canreduce a risk of leakage. Preferably, the heat conductive materialdisposed within the cavities 20 is a liquid or flexible material. In thesituation that the casing is subjected to an external impact force, theexternal impact force can be transmitted to the internal liquid or theflexible material by the cavities 20. Since the liquid or flexiblematerial has a high deformation performance, the external impact forcecan be further absorbed, thereby further improving the impact resistanceof the casing 1.

By forming a plurality of cavities 20 in the wall portion 11, the casing1 for a battery pack provided by the embodiments of the presentdisclosure not only can improve the bearing capacity and impactresistance thereof, but also can realize the thermal management of thebattery assembly 2 by filling the plurality of cavities 20 with thephase change material or cooling liquid, which can further improve theimpact resistance and mechanical property of the casing 1, with a simplestructure, light weight and high reliability.

The specific configuration of the casing 1 for a battery pack providedby the embodiments of the present disclosure will be further describedin detail below with reference to the accompanying drawings.

Referring to FIG. 3, the wall portion 11 of the casing 1 includes abottom wall 111 and side walls 112 surrounding the bottom wall 111 on aperipheral side of the bottom wall 111. Specifically, the bottom wall111 and the side walls 112 of the casing 1 are integrally formed, toimprove a sealing property of the casing 1 and avoid a seal failurebetween the bottom wall 111 and the side walls 112 due to the connectionof the both.

Further, referring again to FIG. 1 and FIG. 2, the casing 1 includes abrim portion 12 extending from the opening of the receiving space 10 ina direction away from a peripheral side of the receiving space 10. Thebrim portion 12 is connected with the cover 3 to form the enclosed spacefor accommodating the battery assembly 2. In the present embodiment, thecasing 1 can be formed by an integral structure of the bottom wall 111,the side walls 112 and the brim portion 12, to further improve thesealing property of the casing 1.

In order to ensure the structural strength of the battery pack andsatisfy the bearing capacity requirements of the battery pack, the metalbase plate is made of materials with a tensile strength σ≥100 Mpa, suchas aluminum, magnesium, iron and alloys thereof with the tensilestrength σ≥100 Mpa, which can avoid too thin part or tensile fracture ofthe casing caused by deformation of the base plate during the formingprocess. Preferably, the material of the base plate has an elongation atbreak ≥12%, which can ensure that the base plate has a certain amount ofdeformation during the process of forming the side walls 112 and thebrim portion 12 of the wall portion 11, thereby ensuring the sealingproperty and strength of the casing 1. Since the battery pack mayencounter a wading environment during use, the side walls 112 shouldhave a height greater than 20 mm, so as to prevent external water fromimmersing into the battery pack.

Referring to FIG. 3 and FIG. 4 together, as described above, the wallportion 11 is formed by two or more stacked base plates. Specifically,the wall portion 11 is formed by two base plates, to further reduce theweight and volume of the casing. The two base plates include a firstbase plate 21 and a second base plate 22. The cavity 20 may be formed byan outwardly projecting convex wall 221 of the second base plate 22 andan outwardly projecting convex wall (not shown) of the first base plate21. Alternatively, the cavity 20 may be formed by an outwardlyprojecting convex wall 221 of the second base plate 22 and a flat wall211 of the first base plate 21 corresponding to the convex wall 221.Therefore, when the battery pack is subjected to an impact, the externalforce acts on the convex wall 221 at first and then is transmitted tothe cavity 20, the second base plate 22 and the first base plate 21 bythe convex wall 221. By such multi-level dispersion of the force, theimpact resistance of the casing 1 can be improved. Preferably, it iseasy to arrange other components (such as support members, protectivemembers) on the casing 1, by forming the cavity 20 by the outwardlyprojecting convex wall 221 of the second base plate 22 and the flat wall211 of the first base plate 21 corresponding to the convex wall 221.

More preferably, the first base plate 21 and the second base plate 22are stacked in a direction from the receiving space 10 to an exterior ofthe casing 1, and thus the flat wall 211 of the first base plate 21 isdisposed close to the battery assembly 2 of the battery pack.Accordingly, a surface of the first base plate 21 close to the batteryassembly 2 is approximately planar, which can increase a contact areabetween the first base plate 21 and the battery assembly 2. As a result,the force transmitted to the battery assembly 2 can be uniformlydispersed, which can avoid a failure of the battery assembly 2 due to alocal excessive external impact force, thereby improving the safety ofthe battery assembly 2.

In order to ensure the sealing of the plurality of cavities 20 formedbetween the base plates, it is preferable that the cavities 20 areformed between the first base plate 21 and the second base plate 22 by ablow molding process. In order to avoid a rupture of the convex wall 221of the cavity 20 during the blow molding process, it is furtherpreferred that the material of the base plate is aluminum or an aluminumalloy having an elongation at break ≥20%. Preferably, the tensilestrength σ1 of the material of the first base plate 21 is equal to orgreater than the tensile strength σ2 of the material of the second baseplate 22, which facilitates controlling the amount of deformation of thefirst base plate 21 and that of the second base plate 22 in the blowmolding process, such that the relatively straight flat wall 211 can beformed in the first base plate 21.

Referring to FIG. 5, the convex wall 221 of the second substrate 22includes a top portion 2211 and a side portion 2212 connected to the topportion 2211. The top portion 2211 is planar or curved, and there is asmooth transition between the top portion 2211 and the side portion2212. The top portion 2211 is preferably planar, which can increase acontact area of the convex wall 221 with an external device, facilitateuniform dispersion of the external force, and prevent the external forcefrom acting on the highest point of the convex wall 221, causingcracking of the convex wall 221. The top portion 2211 and the sideportion 2212 are smoothly transitioned, which facilitates the dispersionof the force and can increase the stability of the convex wall 221,thereby avoiding the convex wall 221 from being deformed or broken dueto excessive local force.

Further, a ratio of a wall thickness t1 of the flat wall 211 to a wallthickness t2 of the convex wall 221 is in a range of 0.5≤t2/t1≤1. Ift2/t1>1, the first base plate 21 will be easily twisted and deformedwhen forming the cavity 20 by the blow molding process, causing that thefirst base plate 21 is deformed at the surface close to the batteryassembly 2 and thus cannot be attached to the battery assembly 2; Ift2/t1<0.5, the convex wall 221 of the second base plate 22 will easilybe broken during use since the convex wall 221 is too thin, causing aseal failure of the cavity 20. A height h of the cavity 20 is in a rangeof h≤5×t1. If the height h>5×t1, the second base plate 22 will be easilybroken in the blow molding process. A ratio of the height h to a width Wof the cavity 20 is in the range of h/W≤0.5, and if the height h is toogreat, the first base plate 21 will be easily twisted and deformed. Ifthe height h is too small, a fluid flow resistance will increase, whichbrings an adverse effect to the thermal management of the batteryassembly 2.

Further, after the casing 1 is press-formed from the metal base plates,a spherical corner 113 is formed between the bottom wall 111 and twoadjacent side walls 112. Since the wall thickness at the sphericalcorner 113 is thin, it is disadvantageous to arrange the cavity 20.Moreover, the spherical corner 113 is easily broken under the impact ofan external force. In order to avoid the sealing of the cavity 20 frombeing affected by the damage of the spherical corner 113, a minimumdistance d from an intersection line between two adjacent side walls 112to the cavity 20 is in a range of d≥25 mm, to weaken the external forcetransmitted from the spherical corner 113 to the cavity 20. For example,in the case that a plurality of cavities 20 are formed in the bottomwall 111, the minimum distance d from the cavity 20 close to one sidewall 112 formed in the bottom wall 111 to the side wall 112 is equal toor greater than 25 mm, to avoid a rupture of the cavity 20 and thus aseal failure due to the spherical corner 113 subjected to an externalforce, as shown in FIG. 4.

As described above, the wall portion 11 of the casing 1 includes abottom wall 111 and side walls 112 surrounding on a peripheral side ofthe bottom wall 111. The cavity 20 may be formed in the bottom wall 111,may be formed in the side walls 112, and may be formed in both thebottom wall 111 and the side walls 112. By reasonably arranging thedistribution and area of the cavities 20, the impact resistance of thebattery pack can be improved. For convenience of description, theembodiments of the present disclosure are described by taking the cavity20 formed in the bottom wall 111 as an example.

Referring to FIGS. 6 and 7 together, the plurality of cavities 20 formedin the bottom wall 111 are in communication with each other to form aflow passage R. An inlet pipe 13 and an outlet pipe 14 are disposed onthe side wall 112 of the casing 1. The inlet pipe 13 and the outlet pipe14 are in communication with two ends of the flow passage R,respectively, and are located on the same side of the side wall 112 toreduce an overall size of the casing 1. The inlet pipe 13 and the outletpipe 14 are identical or similar in structure. Taking the inlet pipe 13as an example to make an illustration, a mounting step 131 and a weldingstep 132 are disposed on the inlet pipe 13 and spaced apart from eachother, wherein the inlet pipe 13 is fixed to the side wall 112 by thewelding step 132, and is electrically connected to an external devicevia the mounting step 131.

As an optional embodiment, the plurality of cavities 20 may form aplurality of liquid inflow channels and a plurality of liquid returnchannels arranged side by side in the bottom wall 111. The plurality ofliquid inflow channels and the plurality of liquid return channels arecommunicated with each other at one ends, and the plurality of liquidinflow channels are connected to the inlet pipe 13 at the other endwhile the plurality of liquid return channels are connected to theoutlet pipe 14 at the other ends, to form a plurality of U-shaped flowpassages in parallel. The thermal management of the entire batteryassembly 2 can be performed by the phase change material or the coolingliquid in the flow passages.

In the situation that the cavities 20 are filled with the coolingliquid, one end of the inlet pipe 13 is connected to a cooling liquidinput device, and an inflow confluence region R1 is formed in the wallportion 11 corresponding to the other end of the inlet pipe 13; and oneend of the outlet pipe 14 is connected to a cooling liquid outputdevice, and an outflow confluence region R2 is formed in the wallportion 11 corresponding to the other end of the outlet pipe 14, whereinthe inflow confluence region R1 and the outflow confluence region R2 areisolated from each other to increase a flow rate of the cooling liquidin each flow channel. As shown in FIG. 7, the inflow confluence regionR1 is a cavity 20 located between the side wall 112 and the bottom wall111, which is formed between the first base plate 21 and the second baseplate 22 by the blow molding process, and the inflow confluence regionR1 is in communication with the plurality of liquid inflow channelsarranged side by side. Similarly, the outflow confluence region R2 is acavity 20 located between the side wall 112 and the bottom wall 111,which is formed between the first base plate 21 and the second baseplate 22 by the blow molding process, and the outflow confluence regionR2 is in communication with the plurality of liquid return channelsarranged side by side. The cooling liquid is introduced into the inflowconfluence region R1 via the inlet pipe 13, and then enters therespective liquid inflow channels arranged side by side along the arrowsin FIG. 6. After that, the cooling liquid turns at the ends of therespective liquid inflow channels, enters the respective liquid returnchannels arranged side by side along the arrows in FIG. 6, and thenconverges at the outflow confluence region R2 at the ends of therespective liquid return channels. Finally, the cooling liquiddischarges from the outlet pipe 14. Since the temperature of the coolingliquid gradually rises during the flow from the inlet pipe 13 to theoutlet pipe 14, the portion of the casing 1 near the liquid inflowchannels generally has a temperature difference from the portion of thecasing 1 near the liquid return channels. Therefore, the abovearrangement of the channels allows the temperature distribution of thebattery assembly 2 to be relatively uniform.

In the situation that the cavities 20 are filled with the phase changematerial, the battery pack is further provided with a temperaturecontrol device to control a temperature of the phase change material. Inthe case that a temperature of the battery assembly 2 in the batterypack is lower than a lowest target temperature, the phase changematerial within the cavities 20 can be heated to change from a solidstate to a liquid state, so that the phase change material can releaseheat and provide the heat to the battery assembly. Thus, the batteryassembly 2 can be rapidly heated especially when the vehicle is parkedin a cold environment. In the case that the temperature of the batteryassembly 2 in the battery pack is higher than a highest targettemperature, the temperature of the phase change material within thecavities 20 can be lowered such that the phase change material canabsorb heat from the battery assembly 2 during transition from theliquid state to the solid state, thereby quickly removing the heat fromthe battery assembly 2. As a result, the temperature distribution of theentire battery assembly 2 can be uniform, and the thermal management ofthe battery assembly 2 can be improved.

Further, in the situation that the cavities 20 are filled with the phasechange material, the plurality of liquid inflow channels and theplurality of liquid return channels arranged side by side may or may notin communication with each other.

It should be noted that the flow passage formed by the plurality ofcavities 20 is not limited to the example shown in FIG. 6, and may be,for example, formed as an S-shaped flow passage, a hollow square shapedflow passage, or the like, and specifically, a path of the flow passageformed by the plurality of cavities 20 may be reasonably arrangeddepending on the configuration of the battery assembly 2 in the batterypack, and more details will not be described here.

Although the above description has been made with the cavities 20 formedin the bottom wall 111 as an example for convenience of description, itshould be understood that the casing 1 according to the exemplaryembodiments of the present disclosure is also applicable to aconfiguration in which the cavities 20 are formed in the side walls 112,and a configuration in which the cavities 20 are formed in both thebottom wall 111 and the side walls 112, and more details will not bedescribed here.

Referring to FIG. 8, an embodiment of the present disclosure furtherprovides a casing 1 for a battery pack, which has a similarconfiguration to the casing 1 as shown in FIG. 3, except that the cavity20 is provided with an island 30 therein.

Referring to FIG. 8 and FIG. 9 together, the description will be made bytaking a plurality of cavities 20 formed in the bottom wall 111 as anexample. The plurality of cavities 20 in the bottom wall 111 are incommunication with each other to form a flow passage R.

The wall portion 11 includes a first base plate 21 and a second baseplate 22 which are stacked in a direction from the receiving space 10 toan exterior of the casing 1. The cavity 20 is formed by an outwardlyprojecting convex wall 221 of the second base plate 22 and a flat wall211 of the first base plate 21 corresponding to the convex wall 221, andthe island 30 is formed by recessing the convex wall 221 toward the flatwall 211. By forming the convex wall 221 and the island 30 in oppositedirections, the rigidity of the second base plate 22 and thus thebearing capacity of the casing 1 can be increased. Further, referring toFIG. 10, the convex wall 221 includes a top portion 2211 and a sideportion 2212 connected with the top portion 2211. The top portion 2211is planar or curved, there is a smooth transition between the topportion 2211 and the side portion 2212, and a portion of the convex wall221 corresponding to the island 30 is attached to the flat wall 211. Anexternal force acting on the convex wall 221 can be partiallytransmitted to the first base plate 21 via the island 30, which canfurther improve the impact resistance of the cavity 20 and of the casing1, and meanwhile can increase a rate of finished products when moldingthe casing 1 and avoiding damage of the casing 1 due to distortiondeformation of the cavity 20. Further, there is a smooth transitionbetween a peripheral side of the island 30 and the convex wall 221,which can reduce a resistance experienced by the cooling liquid or thephase change material in a liquid state when flowing across theperipheral side of the island 30.

Further, when the cavity 20 has the island 30 disposed within it, thecavity 20 has a relatively reduced volume. In order to increase thevolume of the cavity 20, a ratio of a height h of the cavity 20 to awidth W of the cavity 20 can be set in a range of h/W≤1.

The plurality of cavities 20 are in communication with each other toform a flow passage R within which the island 30 is disposed. There maybe multiple islands 30 arranged in one or more rows in a lengthdirection of the flow passage R. The multiple islands 30 can effectivelyenhance a pressure resistance of the cavities 20, and can ensure that aplurality of turbulences are formed by the cooling liquid or the phasechange material in the liquid state flowing through the flow passageformed by the cavities 20, which can make the temperature distributionof the wall portion 11 more uniform, and increase the heat exchangeefficiency of the battery assembly 2.

Referring to FIG. 9, a portion of the island 30 attached to the flatwall 211 is formed in a shape of strip or ellipse, and a long side ofthe strip or a major axis of the ellipse is parallel to the lengthdirection of the flow passage R. During the blow molding process, amedium moves along the length of the flow passage R. By disposing thelong axis of the island 30 along the length direction of the flowpassage R, a rate of finished products when molding the flow passage Rcan be increased. Besides, the stripped or elliptical shape of theisland 30 can relatively increase a contact area between the island 30and the first base plate 21, thereby avoiding deformation of the island30 during the blow molding process.

Preferably, a ratio of a length L of the island 30 to a width W1 of theisland 30 is in a range of 2≤L/W1≤5, wherein the length L is in a rangeof 5 mm≤L≤15 mm. If the length or width of the island 30 is too large, aflow resistance in the cavity 20 will be increased, and if the length orwidth of the island 30 is too small, the cavity 20 will be easily brokenduring the blow molding process, or a structural strength of the cavity20 will be insufficient.

A first space L1 is defined as a distance from a center of the island 30to one side of the cavity 20, and the first space L1 is equal to orgreater than the width W1 of the island 30. When the multiple islands 30are arranged in two or more rows in the length direction of the flowpassage R (that is, there may be two or more islands 30 spaced apartfrom each other in a direction perpendicular to the length direction ofthe flow passage R in a certain cross section of the cavity 20, comparedto the case that there is only one island in the cross section of onecavity 20 as shown in FIG. 10), a distance between the centers of theislands 30 in two adjacent rows can be defined as a third space L3, anda distance from a center of the island 30 closest to a side of thecavity 20 to the side of the cavity 20 can be regarded as the firstspace L1, wherein L3≥W1 and L1≥W1. If L1<W1 or L3<W1, the cavity 20 willbe easily broken during the blow molding process.

A second space L2 is defined as a distance between two adjacent islands30 in each row in the length direction of the flow passage R.Preferably, the second space L2 is equal to or greater than the firstspace L1, and if the second space L2 is smaller than the first space L1,the cavity 20 will be easily broken during the blow molding process.

By providing the islands 30 in the plurality of cavities 20 in the wallportion 11, the casing 1 for a battery pack provided by the embodimentsof the present disclosure can not only improve the structural strengthof the casing 1 and of the cavities 20, but also can change a flowcapacity and a flow rate of the fluid in the cavities 20, which can makethe temperature distribution of the wall portion 11 more uniform,increase the heat exchange efficiency of the battery assembly 2, andfurther improve the thermal management of the battery pack.

Referring again to FIG. 2, the casing 1 for the battery pack accordingto any of the above-mentioned embodiments includes a support member 15fixed to the bottom wall 111. The support member 15 is provided with aplurality of threaded holes, and a fixing frame of the battery assembly2 is provided with through holes. The battery assembly 2 can be fixed inthe receiving space 10 by passing screws through the threaded holes andthe through holes. The cover 3 can close the opening of the casing 1 toform an enclosed space for accommodating the battery assembly 2 togetherwith the receiving space 10 of the casing 1.

In order to further improve the thermal management of the batteryassembly 2, a thermal conductive adhesive can be applied between aninner surface of the bottom wall 111 and the battery assembly 2, toallow heat to be rapidly transferred between the battery assembly 2 andthe cavities 20.

The casing 1 further includes a protective member 16, which is kept awayfrom the cavities 20 and fixed at an edge of the casing 1, to supportthe entire casing 1 and protect the cavities 20 from being damaged byexternal components. Also, the battery pack can be fixed to the vehicleor other components via the protective member 16.

Further, the embodiments of the present disclosure further provide abattery pack comprising a casing 1 according to any one of theembodiments as described above, in which the heat exchange efficiency ofthe battery assembly 2 can be increased and the thermal management canbe improved.

Although the present disclosure has been described with reference to thepreferred embodiments, various modifications may be made to the presentdisclosure and components may be replaced with equivalents withoutdeparting from the scope of the present disclosure. In particular, thetechnical features mentioned in the various embodiments can be combinedin any manner as long as there is no structural conflict. The presentdisclosure is not limited to the specific embodiments disclosed herein,but includes all technical solutions falling within the scope of theclaims.

What is claimed is:
 1. A casing for a battery pack, wherein the casinghas a receiving space and an opening in communication with the receivingspace, the receiving space is formed by a wall portion of the casing,and the wall portion is formed from two or more stacked base plates,between which a plurality of cavities are formed, wherein the baseplates comprises a first base plate and a second base plate, and thecavity is formed by an outwardly projecting convex wall of the secondbase plate and a flat wall of the first base plate corresponding to theconvex wall, wherein the flat wall has a wall thickness t1 and thecavity has a height h in a range of h≤5×t1.
 2. The casing according toclaim 1, wherein the first base plate and the second base plate arestacked in a direction from the receiving space to an exterior of thecasing.
 3. The casing according to claim 1, wherein the convex wallcomprises a top portion and a side portion connected to the top portion,wherein the top portion is planar or curved, and there is a smoothtransition between the top portion and the side portion.
 4. The casingaccording to claim 1, wherein the wall portion has a wall thickness t ina range of 1 mm≤t≤6 mm.
 5. The casing according to claim 1, wherein aratio of a wall thickness t1 of the flat wall to a wall thickness t2 ofthe convex wall is in a range of 0.5≤t2/t1≤1.
 6. The casing according toclaim 1, wherein a ratio of the height h to a width W of the cavity isin a range of h/W≤0.5.
 7. The casing according to claim 1, wherein thewall portion comprises a bottom wall and side walls surrounding thebottom wall on a peripheral side of the bottom wall, and the bottom walland the side walls are integrally formed.
 8. The casing according toclaim 7, wherein a minimum distance d from an intersection line betweentwo adjacent side walls to the cavity is equal to or greater than 25 mm.9. The casing according to claim 7, wherein the plurality of cavitiesare in communication with each other to form a flow passage.
 10. Thecasing according to claim 9, wherein the casing is provided with aninlet pipe and an outlet pipe on one of the side walls, wherein theinlet pipe and the outlet pipe are respectively in communication withtwo ends of the flow passage, and are located at a same side of the sidewall.
 11. The casing according to claim 1, wherein a material of thebase plate has a tensile strength σ≥100 MPa, and has an elongation atbreak ≥12%.
 12. The casing according to claim 11, wherein the materialof the base plate has an elongation at break ≥20%.
 13. The casingaccording to claim 1, wherein the cavities are formed between the firstbase plate and the second base plate by a blow molding process.
 14. Abattery pack, comprising: a battery assembly; a casing having areceiving space and an opening in communication with the receivingspace, the receiving space is formed by a wall portion of the casing,and the wall portion is formed from two or more stacked base plates,between which a plurality of cavities are formed; and a cover closingthe opening of the casing to form an enclosed space for accommodatingthe battery assembly together with the receiving space of the casing,wherein the base plates comprises a first base plate and a second baseplate, and the cavity is formed by an outwardly projecting convex wallof the second base plate and a flat wall of the first base platecorresponding to the convex wall, wherein the flat wall has a wallthickness t1 and the cavity has a height h in a range of h≤5×t1.
 15. Thebattery pack according to claim 14, wherein the first base plate and thesecond base plate are stacked in a direction from the receiving space toan exterior of the casing.
 16. The battery pack according to claim 14,wherein the convex wall comprises a top portion and a side portionconnected to the top portion, wherein the top portion is planar orcurved, and there is a smooth transition between the top portion and theside portion.
 17. The battery pack according to claim 14, wherein thewall portion has a wall thickness t in a range of 1 mm≤t≤6 mm.
 18. Thebattery pack according to claim 14, wherein a ratio of a wall thicknesst1 of the flat wall to a wall thickness t2 of the convex wall is in arange of 0.5≤t2/t1≤1.
 19. The battery pack according to claim 14,wherein a ratio of the height h to a width W of the cavity is in a rangeof h/W≤0.5.
 20. The battery pack according to claim 14, wherein the wallportion comprises a bottom wall and side walls surrounding the bottomwall on a peripheral side of the bottom wall, and the bottom wall andthe side walls are integrally formed.